As more computing power and new functions are added to mobile computing devices, new auxiliary devices are being attached to the mobile computing devices. The mobile computing devices may include, for example, laptop computers, personal digital assistants (PDAs), and mobile phones, among others. The auxiliary devices may include universal serial bus (USB) drives, digital video disk (DVD) drives, compact disk (CD) drives, and moving picture expert group (MPEG) based devices, among other current and future auxiliary devices.
A mobile computing device is normally configured with a portable power source such as a rechargeable battery. The portable power source of the mobile computing device supplies the power not only to the mobile computing device, but may also supply power to an attached auxiliary device. Because the portable power source has a limited amount of power, such as when no alternating current (AC) power is available, there may be a contention for power among the mobile computing device and the attached auxiliary devices.